Evaluation of forest grasses as livestock feed

M P S Bakshi, M P Singh, M Wadhwa and B Singh*

Department of Animal Nutrition, Punjab Agricultural University, Ludhiana-141004, India
*DCN, National Dairy Research Institute, Karnal-132001
bakshimps@yahoo.com

Abstract

Ten wild forest grasses, Taraxacum purpureum, Sancharum spontaneum, Bansari, Kahi, Olea ferruginea,Saccarum munja, Eulaliopsis binata, Chrysopogon aciculatus, Tholu and Badewan, were evaluated for their nutritional worth for livestock feeding. The samples were collected at 30d intervalsfor 12m. The finely ground samples were pooled for different seasons viz. dry-hot, hot humid, fall and winter.

The OM, CP, NDF and ADL content ranged between 88 to 93.5%, 4.7 to 8.3%, 76.9 to 87.8% and 6.75 to 9.87%, respectively. Taraxacum grass had the lowest ADL and cell wall constituents. Maximum concentration of NDF, ADF and cellulose was observed in hot humid season. Most of the grasses were rich in Ca and Mg, but highly deficient in P and trace minerals. The level of water soluble oxalates, total-, condensed- or hydrolysable-tannins was very low. Taraxacum and Sancharum had high 48 h degradability and effective degradability, and  had low rumen fill values, indicating their potential for high voluntary dry matter intake. Season showed no significant effect on the digestion kinetic parameters. All the grasses had nutritive value index above 30.

Key words: anti nutritional factors, digestion, nutritive value index, wild grasses

Introduction

India is the world's seventh largest (328.7 million ha) and one of the most populated (over 1000 million) countries, supporting 16 percent of the planet's human population and 18 percent of the cattle population. Our nation occupies number one position, in milk production, in the world, but the per capita production is very low. The main reason for such low productivity of our livestock is malnutrition, under- nutrition or both, in addition to low genetic potential. Keeping in view, the huge deficit in the availability of feedstuffs (44 MT of crop residues, 280 MT of green fodder and 26 MT of concentrate) and annual population growth rate of 2.35 percent (Anonymous 2000), the possibility of improvement in nutritional status of the animals seems rather bleak. The situation worsens in the semi- hilly arid zones of our country. The animals in such areas are largely dependent on the tree leaves and natural grasses available in these forests, but without knowing the actual nutritional worth of such feed resources.

A comprehensive study, from our laboratory, revealed that some of the forest tree leaves are highly nutritious and showed great potential as an alternate feed resource (Bakshi and Wadhwa 2004). However, animals refuse to eat certain tree leaves in a particular season, mainly because of high concentration of condensed tannins (Rana et al 2005). The objective to take up this study was to know about the potential of the commonly fed wild grasses and the constraints, which limit their extensive use as livestock feed.

Materials and methods

Material selected

Ten wild grasses,viz. Taraxacum purpureum, Sancharum spontaneum, Bansari, Kahi, Olea ferruginea,Saccarum munja, Eulaliopsis binata, Chrysopogon aciculatus, Tholu and Badewan, commonly fed to livestock in the semi-hilly arid zone of Punjab State, were collected at 30 d intervals for 12 months and dried in a forced air oven at 60ºC for 48 h. The ground samples were pooled according to season viz. dry hot (April to June), hot humid (July to September), fall (October to December) and winter (January to March).

Analytical methods

The samples of wild grasses were analysed for proximate components like total ash, crude protein and ether extract (AOAC 1995), cellulose (Crampton and Maynard 1938) and other cell wall constituents (Robertson and Van Soest 1981). Organic matter was calculated by subtracting total ash from 100 and hemicellulose by subtracting acid detergent fiber from neutral detergent fiber. The fat and pigments were removed by extracting the ground grasses with petroleum ether containing 1% acetic acid using Soxhlet apparatus (AOAC 1995). Tannins were extracted, from fat free samples, using 70 per cent aqueous acetone. The contents were centrifuged (at 3000g (4ºC) for 10 min.) and the supernatant was taken for determination of tannins by Folin-Ciocalteu reagent using tannic acid as a standard (Makkar et al 1993). Condensed tannins were determined by using Butanol-HCl (Porter et al 1986). The hydrolysable tannins were calculated by subtracting the condensed tannins from total tannins. For the estimation of water soluble oxalates, the oxalates present in the test samples were extracted in water, precipitated with calcium chloride, which were dissolved in sulphuric acid and titrated with KMnO₄ (Abaza et al 1968). For the estimation of trace elements the samples were digested (AOAC 1980) in triplicate with tri-acid mixture (HNO₃: H₂SO₄: HClO₄ in 15:2:4 ratio) initially at 120ºC for one and a half hours and then the temperature of the digester was increased to 270ºC for another 2 hours. When the solution became clear it was cooled and filtered through Whatman # 42 filter paper. The extractable aliquots were used for the estimation of Zn, Fe, Cu, Mn and Co by Atomic Absorption Spectrophotometer, while calcium by AOAC (1995) and phosphorus was determined by colorimetric method (Jackson 1987).

In sacco studies

Three adult male rumen fistulated buffaloes (live weight 387 ± 25 kg) were maintained on 1.5 kg concentrate mixture (maize 15, wheat 15, mustard cake 20, groundnut cake 10, rice bran 10, deoiled rice polish 27, mineral mixture 2, salt 1 part each), 5 kg wheat straw and 2 kg green fodder, to meet their nutrient requirements (NRC 2001), 30 days before starting the in sacco evaluation.

The parachute nylon bags (8x15 cm; 50±10 μm pore size), containing 3 gm ground test sample in triplicate, were incubated in the rumen of three rumen fistulated male buffaloes, for 0, 3, 6, 9, 12, 24, 36, 48, 60 and 72 h (Mehrez and Ørskov 1977). On removal, the bags were washed under running tap water till the rinsing water became colourless. The bags after squeezing gently were dried at 55ºC for 48 h. The disappearance of DM was calculated from the amount incubated and left in the bag at each incubation period. The residue was analysed for NDF for determining the rate and extent of digestion in the rumen. The different parameters, characterizing extent and rate of ruminal degradation i.e. `A' rapidly soluble fraction, `B' insoluble but degradable fraction and `C' degradation rate, were calculated according to Ørskov et al (1988). The effective degradability was estimated according to McDonald (1981). The rumen fill values were calculated by using the equation of Van Eys (1982).

Statistical analysis

The data were analysed by following 10x4 factorial and completely randomised designs (Snedecor and Cochran 1994) by using STATGRAPHICS version 5.0. The means were compared for statistical significance by using Duncan's multiple range test (Duncan 1955).

Results and discussion

Chemical composition

The proximate composition of different grasses irrespective of season revealed that the organic matter (Table1) of wild grasses ranged between 88% (Taraxacum) to 93.5% (Kahi). The CP content ranged between 4.7 to 8.3%. Kahi had the lowest (P<0.05) and Taraxacum had the highest crude protein content. The highest (P<0.05) EE content was observed in Olea grass and lowest in Eulaliopsis.

The NDF content was minimum (P<0.05) in Taraxacum and maximum concentration (P<0.05) was observed in Saccarum (Table 1). These grasses, Saccarum, Kahi and Bansari differed significantly (P<0.05) from Olea and Badewan. The highest ADF (lignocellulose complex) content was observed in Chrysopogon which was comparable with that of Saccarum and Tholu. The lignin content ranged between 6.75 to 9.87%. Tholu, Olea, Saccarum, Bansari and Badewan had more than 9% lignin content, whereas Taraxacum had the lowest lignin as well as cell wall constituents. The lignin and NDF contents were observed to be positively correlated (r = 0.57).

The season had significant (P<0.05) but inconsistent effect on various proximate and cell wall components (Figures1 and 2).

OM and EE contents were significantly (P<0.05) higher in dry hot season as compared to extreme winter. However, the  reverse trend was observed in ADF (P<0.05) and lignin.

The maximum concentrations of NDF, ADF and cellulose were observed during hot-humid season.

Mineral status

The mineral profile (Table 2) of wild grasses indicated that the calcium and phosphorus content ranged between 0.77 to 1.45% and 0.06 to 0.14%, respectively.

Saccarum had the highest concentration of calcium, which was comparable with that of Taraxacum, Sancharum and kahi. Chrysopogon had the lowest concentration of calcium. The highest concentration of phosphorus was observed in Sancharum followed by Badewan, Tholu and Chrysopogon. Chrysopogon showed the presence of high amount of Fe, Mg, and Mn (0.066, 35.78 and 0.207 ppm, respectively) amongst the grasses evaluated. Maximum concentration of Co, and Zn was observed in Taraxacum. Cu content of wild natural grasses ranged between 0.069 to 0.073 ppm. In comparison to NRC (2001) recommendations for complete feed for dairy cattle, most of the wild grasses were found to be rich in Ca and Mg (beyond tolerance limits), but highly deficient in P and most of the trace elements. It is therefore recommended that animals of such areas must be provided quality mineral mixture, to avoid the mineral deficiency.

Anti nutritional factors

The water-soluble oxalate content of wild grasses ranged between 0.51 to 1.29 per cent. Bansari had the highest concentration while Chrysopogon had the lowest concentration. The values were well below the toxic levels of 4% (Lal et al 1966). The total tannin content in grasses ranged between 0.49 to 1.36 per cent. Sancharum had the highest concentration followed by Taraxacum and Badewan grasses. Saccarum had the lowest concentration. In all the grasses studied, hydrolysable tannins constituted about 95.5 to 99.0% of total tannins (Figure 3) with negligible concentration of condensed tannins. The low levels of tannins present in above grasses may be beneficial in preventing frothy bloat (Li et al 1996).

The presence of tannins (TT, CT or HT) had no adverse effect on the 48h degradability of dry matter or NDF, as indicated by positive correlations (0.72, 0.51, 0.69 for DM and 0.69, 0.56, 0.67 for NDF) between these parameters, however the NDF and TT were negatively correlated (-0.61). The only plausible explanation is that the level of these anti nutritional factors was too low to affect degradability of grasses.

Digestion kinetics for dry matter

The digestion kinetics for DM of different grasses, irrespective of season (Table 3, Figure 4) indicated that Tholu had the lowest (P<0.05) and Eulaliopsis had the highest (P<0.05) rapidly soluble fraction.

The potentially degradable fraction was found to be maximum (P<0.05) in Sancharum. Saccarum had significantly (P<0.05) lower potentially degradable fraction. The faster degradation rate of potentially degradable fraction (Table 3) was responsible for significantly low (P<0.05) un-degradable fraction in Sancharum and Taraxacum. These parameters were responsible for significantly (P<0.05) higher 48 h and effective DM degradability, with significantly low (P<0.05) rumen fill (Table 3).

The low rumen fill value indicated higher potential for predicted voluntary DM intake. On the contrary, the significantly (P<0.05) lower potentially degradable fraction in Sancharum with slow degradation rate were responsible for poorest (P<0.05) effective degradability and significantly (P<0.05) high rumen fill, which resulted in the lowest potential for voluntary DM intake. The nutritive value index (NVI), when worked out from digestion kinetic parameters (A, B and C), revealed that all the grasses had NVI above 30, except for Sancharum (28.7). The 48h degradability of dry matter was found negatively correlated with ADF (-0.78), NDF (-0.77) and lignin (-0.71) content. The seasons showed no significant effect on the digestion kinetics for DM (Figure 5).

However, maximum potentially degradable fraction was observed in grasses, during dry hot season as compared to extreme winter. The potential degradable fraction gets degraded at a faster rate during this season. The highest un-degradable fraction during fall was responsible for higher rumen fill values, which indicated poor potential for voluntary DM intake. The maximum 48 hour and effective degradability of grasses' DM and that of fibre was during dry hot and fall, respectively (Figure 8). The NVI of wild grasses, ranged from 38.6 to 40.9, quite above the value recommended (~30), which indicate that intake of the feed will be sufficient to enable maintenance. Sood et al (1975) evaluated 10 species of grasses and reported that they had high NVI (43.35 to 61.37%).

Digestion kinetics for Neutral Detergent Fibre (NDF)

The digestion kinetics of grasses for NDF, irrespective of seasons, (Table 3, Figure 6) indicated that Eulaliopsis had the highest (P<0.05) rapidly soluble fraction, followed by that in Badewan.

The negative values for rapidly soluble fraction in Tholu and Sancharum the presence of lag phase for initiation of microbial colonization/degradation. Sancharum and Taraxacum had comparable and the highest (P<0.05) potentially degradable fraction. The faster (P<0.05) degradation rate of potentially degradable fraction was responsible for higher (P<0.05) effective NDF degradability resulting in lower (P<0.05) un-degradable fraction of NDF. On the contrary, Saccarum had the lowest (P<0.05) potentially degradable fraction comparable to Bansari, and Badewan. The significantly slow rate of degradation of these grasses was responsible for their low effective degradability, resulting in considerably higher un-degradable fraction of NDF. The rumen fill values worked out for these wild grasses revealed that Saccarum had the highest value responsible for its' low potential for voluntary intake of NDF, whereas reverse trend was observed in Taraxacum and Sancharum. The 48h degradability of NDF was found to be negatively correlated with CWC (-0.83 ADF, -0.70 NDF and -0.72 lignin). The NVI, worked out on the basis of digestion kinetic parameters for NDF, revealed that all the grasses had value above 30 except for Chrysopogon and Saccarum, clearly indicating that some of the grasses like Taraxacum, Sancharum, Badewan, Eulaliopsis, and Olea have great potential as livestock feed.

The season had no significant effect on the digestion kinetics for NDF (Figure 7).

On an average, maximum potentially degradable fraction was observed in grasses during dry hot season and minimum during fall. Reverse trend was observed in rapidly soluble fraction. The 48h degradability and effective degradability of NDF of grasses, was observed to be highest in dry hot and fall, respectively (Figure 8).

The high effective degradability during dry hot months and low rumen fill values during this period led to high potential for voluntary intake of NDF. The NVI of wild grasses varied from 33.6 to 36.1, being highest during fall and lowest during dry hot season.

Conclusions

• On the basis of chemical composition, presence of anti-nutritional factors, 48h degradability, digestion kinetic parameters and NVI, grasses like Taraxacum and Sancharum showed great potential as livestock feed.

References

Abaza R H, Blake J T and Fisher E J 1968 Oxalate determination: Analytical problems encountered with certain plant species. Journal of the Association of Official Analytical Chemists 51: 963-67.

Anonymous 2000 World Fact Book, quoted by Devendra P In 'Trees Outside Forests: India-Towards Better Awareness'.

AOAC 1980 Official Methods of Analysis, 15^th edition Association of Official Analytical Chemists, Washington, D.C.

AOAC 1995 Official Methods of Analysis, Association of Official Analytical Chemists, Arlington, Virginia, USA.

Bakshi M P S and Wadhwa M 2004 Evaluation of forest tree leaves of semi-hilly arid region as livestock feed. Asian Australasian Journal of Animal Science 17: 777-783.

Crampton E W and Maynard L A 1938  The relation of cellulose and lignin content to the nutritive value of animal feeds. Journal of Nutrition 15 : 383-95.

Duncan D B 1955 Multiple range and F tests. Biometrics, 11: 1-42

Jackson M L 1987 Soil Chemical Analysis. Prentice Hall of India, New Delhi.

Lal B M, Johri R P and Mehta R K 1966 Some investigations on the oxalate status of pusa giant napier grass and its parents. Current Sciences 35:125-28

Li Y G, Tanner G and Larkin J 1996 The DMCA-Hcl protocol and the threshold proanthocynanidin content of bloat safety in forage legumes. Journal of the Science of Food and Agriculture 70:89-101

Makkar H P S, Blummel M, Borowy W K and Becker 1993 Gravimetric determination of tannins and their correlations with chemical and precipitation methods. Journal of the Science of Food and Agriculture 61: 161-65

McDonald J 1981 A revised model for the estimation of protein degradability in the rumen. Journal of Agricultural Science Cambridge 96: 251-52.

Mehrez A Z and Orskov E R 1977 A study of artificial fibre-bag technique for determining digestibility of feeds in the rumen. Journal of Agricultural Science Cambridge 88: 645-50.

NRC 2001 Nutrient Requirements of Dairy Cattle. 7^th edition National Research Council, National Academy Press, Washington, D.C., U.S.A.

Orskov E R, Reid G W and Kay M 1988 Prediction of intake by cattle from degradation characteristics of roughages. Animal Production 46: 29-34.

Porter L J, L N Hrstich and Chan B G 1986 The conversion of procyanidins and prodelphinidins to cyaniding and delphinidin. Phytochemistry, 25:223-230.

Rana K K, Wadhwa M and Bakshi M P S 2005 Nutritional quality of tree leaves as affected by season. Asian Australasian Journal of Animal Science 18:(in press)

Robertson J B and VanSoest P J 1981 The detergent system of analysis and its application to human foods. In: Analysis of Dietary Fibre in Food (Editors: W P T James and O Theander). Marcel Dekker Inc., New York. Pp. 123-58.

Snedecor G W and Cochran W G 1994 Statistical Methods. Oxford and IBH Publishing Company, Bombay.

Sood D R, Luthra Y P, Arora S K and Ahuja A K 1975 Variability in chemical composition of grasses and its correlation with nutritive value index. Indian Veterinary Journal 52:711-14

Van Eys J E 1982 Ruminal digestion of tail fescue red clover herbage. Ph.D. dissertation, West Virginia University, Morgantown.